This section is intended to provide background information to facilitate a better understanding of the various aspects of the described embodiments. Accordingly, it should be understood that these statements are to be read in this light and not as admissions of prior art.
Drilling a wellbore for hydrocarbons requires significant expenditures of manpower and equipment. Thus, constant advances are being sought to reduce any downtime of equipment and expedite any repairs that become necessary. Rotating equipment requires maintenance as the drilling environment produces forces, elevated temperatures and abrasive cuttings detrimental to the longevity of seals, bearings, and packing elements.
In a typical drilling operation, a drill bit is attached to a drill pipe. Thereafter, a drive unit rotates the drill pipe through a drive member, such as a kelly, as the drill pipe and drill bit are urged downward to form the wellbore. In some arrangements, a kelly is not used, thereby allowing the drive unit to attach directly to the drill pipe or tubular. The length of the wellbore is determined by the location of the hydrocarbon formations. In many instances, the formations produce fluid pressure that may be a hazard to the drilling crew and equipment unless properly controlled.
Several components are used to control the fluid pressure. Typically, one or more blowout preventers (BOP) are mounted with the well forming a BOP stack to seal the well. In particular, an annular BOP is used to selectively seal the lower portions of the well from a tubular that allows the discharge of mud. In many instances, a rotating control device or rotating control head is mounted above the annular BOP or the BOP stack. An inner portion or member of the rotating control device is designed to seal and rotate with the drill pipe. The inner portion or member typically includes at least one internal sealing element mounted with a plurality of bearings in the rotating control device.
During the drilling operation, the drill pipe or tubular is axially and slidably moved through the rotating control device. The axial movement of the drill pipe along with other forces experienced in the drilling operation, some of which are discussed below, causes wear and tear on the bearing and packer or seal assembly such that the rotating control device subsequently requires repair. Further, the thrust generated by the wellbore fluid pressure, the radial forces on the bearing assembly, and other forces cause a substantial amount of heat to build in the conventional rotating control device. The heat causes the seals and bearings to wear and subsequently require repair. Further, the rotating control device is normally used in the presence of drilling fluid, and in the case of offshore environments, seawater. These fluids can have a high salinity content and also be corrosive, further adding to the potential need to monitor and properly maintain the components of the rotating control device.